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Agricultural tyres in practice

Technical Sales Training 2010. Agricultural tyres in practice. Agricultural tyres in practice List of Content part I. Part I - Tyre conversion Wheel factor Gear factor Forward motion. Agricultural tyres in practice List of c ontent part II. Part II - Adopted tyre pressure

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Agricultural tyres in practice

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  1. Technical Sales Training 2010 Agricultural tyres in practice

  2. Agricultural tyres in practiceList of Content part I Part I - Tyre conversion Wheelfactor Gearfactor Forward motion

  3. Agricultural tyres in practiceList of contentpart II Part II - Adopted tyre pressure Traction Foot print Wheelload & weightdistribution

  4. Agricultural tyres in practiceIntroduction Functions of a tyre • Transmission of forces • driving and breaking forces • lateral guided forces • weight-forces • Cushioning of unevenness • Absorb vibrations INFLATION PRESSURE

  5. Agricultural tyres in practiceTyre conversion Page 112-115 Technical Databook Continental 2010/2011

  6. Tyres previously fitted New tyres Same rim possible Comments Possible per axle Check rim width with 65% tyres Same diameter Cross-ply Radial Standard 85%, 70%, 65% Yes Possible per axle Check rim width with 65% tyres Same diameter Radial Standard 85%, 70%, 65% Yes Possible per axle New rims required Rolling circumferences must match (±2,5%) Same diameter Radial Standard 85%, 70%, 65% Radial Superwide No Possible per axle New rims required Rolling circumferences must match (±2,5%) Same diameter Radial Standard 85%, 70%, 65% Row crop tyres No Only possible for RA and FA New rims required Wheel factors must match original tyres (±2,5%) Unequal diameter Radial Standard 85%, 70%, 65% Row crop tyres No Agricultural tyres in practiceTyre conversion Changing tractor tyres

  7. Examples: 460/85 R 38380/85 R 28 5280 mm4050 mm = 1.30(Original tyres) 520/75 R 38420/75 R 28 5248 mm4056 mm = 1.29(wide tyres with same diameter) 650/65 R 38540/65 R 28 5445 mm 4210 mm = 1.29(wide tyres with different diameter) Agricultural tyres in practice1. Wheel factor Determining the wheel factor Wheel factor = Rolling circumference RA (RCrear)Rolling circumference FA (RCfront)

  8. Agricultural tyres in practice1. Wheel factor Switching to row crop tyres FA-tyres remain, RA-tyres are changed Row crop tyres must have the same rolling circumference as the original tyres. FA-tyres and RA-tyres are changed Row crop tyres “should” have the same rolling circumference as the original tyres. The wheel factor RA to FA must be maintained (max. deviation 2.5%). Example: Original tyre 460/85 R 38 : 380/85 R 28 = 5280 : 4050 = 1.303 Row crop tyres 270/95 R 48 : 270/80 R 36 = 5220 : 4015 = 1.300 1st option 2nd option

  9. Agricultural tyres in practice2. Gear factor What is the GEAR FACTOR?

  10. Agricultural tyres in practice2. Gear factor Rearaxle Front axle The front wheels of a tractor are smaller than the wheels on the rear axle. At the same driving distance the number of wheel revolutions is different on front and rear axle. A differential gear unit has to be installed between both driven axles to compensate this difference. The gear ratio of this differential is called „gear factor“. Differentialgearunitwithtransmission Technicalsolution

  11. Agricultural tyres in practice2. Gear factor Example 1 revolution 1,314 revolutions The GEAR FACTOR isgivenby the tractormanufacturer. Thisdifferenceofrevolutionshastobekeptwith the tyre equipmentasexactlyaspossible. The tyre specialisthastochoose the correct tyre pairing!!!!

  12. Agricultural tyres in practice3. Forward motion To achieve an optimal all wheel driving force, all 4 wheels should run with the same circumferential speed: RCfront x gear factor = RCrear Is an exact synchronisation possible in practice? NO! As the front axle has to compensate this, the tractor manufacturers specify a forward motion of 0% to 5%.

  13. Agricultural tyres in practice3. Forward motion • The correct or allowed advance is the basis for: • basic function of the all-wheel drive (AWD) • efficient traction • durability of tyres • The advance is mainly effected by the RC of the tyres and that is depending on: • the inflation pressure • the wear of the tyre • the wheel load

  14. Influence of the FORWARD MOTION Agricultural tyres in practice3. Forward motion NEGATIV RA is braked by FA! ADVANCE All 4 driven wheels work synchronous, traction is efficient POSITIV 0% to 4% FA is braked by RA ! POSITIV > 6%

  15. Agricultural tyres in practice3. Forward motion Effectsofincorrect FORWARD MOTION • no effective traction • increased fuel consumption • increased tyre wear • damage to the turf due to slip • increased wear or even damage on power train

  16. Agricultural tyres in practice3. Forward motion Determining the FORWARD MOTION 1. Measuring the rolling circumferences and determining the wheel factor with all-wheel drive (AWD) • Switch onall-wheel drive • Mark the centre of the ground contact patch on the ground and the side of the tyre • Mark each wheel revolution of the front and the rear axle on the ground • Drive the tractor forward by at least 5 rear wheel revolutions • Measure the distance covered by the front and rear wheels in each case • Rolling circumference = Distance covered divided by the number of wheel revolutions • Wheel factor = Rolling circumference rear axle (RC rear) Rolling circumference frant axle (RC front) 2. Measuring the rolling circumferences and determining the wheel factor without all-wheel drive • Switch off all-wheel drive and follow the steps above Distance after min. 5 revolutionsof front wheel Distance after min. 5 revolutionsofrearwheel

  17. Agricultural tyres in practice3. Forward motion Forward motion (practical and theoretical approach) • Practical calculation of advance in % Advance = x 100 Example: x 100 = 3.1% • Wheel factor with AWD – Wheel factor without AWD • Wheel factor without AWD • 1.33 – 1.29 • 1.29 • Theoretical calculation of lead in % with known gear factor of the tractor Advance =x 100 • RC front x gear factor – RC rear • RC rear

  18. Agricultural tyres in practice3. Forward motion Determinationof tyre combination RC rear gearfactor (i) RCfront (theor.) = Example: RCrear = 5.420 mm (e.g. 650/65R38) i = 1,314 RCfront (min) = 5.420 / 1,314 = 4.125 mm RCfront (max) = 4.125 + 4% = 4.290 mm

  19. Agricultural tyres in practice3. Forward motion

  20. Width, diameter, infla- tion pressure, design State, density Ground type, moisture Static and dynamic Contact area pressure Contact patch geometry Firmness Agricultural tyres in practice1. Traction Factors influencing transmission of tractive force Tyre Wheel load Ground Contact area Shearing resistance Pressure resistance Positive fit Grip Tractive force – Slip – Performance

  21. Agricultural tyres in practice1. Traction • Preconditions for optimum • transmission of tractive force: • Suitable lug height • Good self-cleaning characteristics • Large tyre diameter • High volume of air for low inflation pressures • Load capacity reserves for add-on weights

  22. Agricultural tyres in practice1. Traction Technical Databook Please see also additional advices on page 94 – 97 of Technical Databook Continental 2010/11

  23. Agricultural tyres in practice1. Traction Traction – dependent on inflation pressure

  24. Agricultural tyres in practice1. Traction Ground contact patches at identical load but different inflation pressure Source: FH Soest, www.Reifenregler.de 0,6 bar 1,6 bar

  25. Agricultural tyres in practice1. Traction Lanes Flat lanes not only protect the ground, it also saves fuel, directly at driving and indirectly because less force is needed for loosening the soil later on. Rule of thumb: 1 cm rut depth = + 10% fuel Source: FH Soest, www.Reifenregler.de

  26. Agricultural tyres in practice1. Traction Slip • Slip is the loss of distance covered, given as percentage. • Slip is hardly noticeable up to a value of approximately 20%. This value corresponds with normal field work. • Slip can be reduced by • Increasing the tractor weight (add-on weights, filling the tyres with water) • Using high-volume or twin tyres • Using hydraulic controls • Adapted tyre inflation pressure

  27. 50% 40% 30% 15% Agricultural tyres in practice1. Traction Loss of distance covered with different degrees of slip:

  28. Agricultural tyres in practice1. Traction Working out the economics Comparison of tractor tyres in heavy tractive work at different slip values Vehicle: 240 hp tractor, operating costs approx. 50 Euro/h Tyre: RA 650/65 R 42, FA 600/65 R 34 Use:Ploughing 300 hectares / 741 acres Working out the economic data: 7 km/h x 2 m = 1.4 ha/h x 0.65*) = 0.91 ha/h 7 km/h x 2 m = 1.4 ha/h x 0.85*) = 1.19 ha/h Slip: 35% 15% a) b) a) 300 ha x h = 330 h x € 50 = € 16,500 0.91 ha b)300 ha x h = 252 h x € 50 = € 12,600 1.19 ha  Savings = € 3,900 *) 35% slip means 0.65 efficiency,15% slip means 0.85

  29. 65 Series Super Volume Agricultural tyres in practice2. Footprint Gentle ground handling Increase of air volume:smaller rim at same outer diameter Ground contact patch Reduction of rim diameter 4600 kg at 30 km/h

  30. Agricultural tyres in practice2. Footprint Gentle ground handling Comparison of ground pressure Bias Radial

  31. 1,2 1,0 0,8 0,6 0,4 0,2 Agricultural tyres in practice2. Footprint Gentle ground handling • The contact patch pressure between the tyre and the ground creates compressive strain in the ground. • This compressive strain leads to an increase in ground compactness and reduces the proportion of air and water pores in the ground. Lines of identical pressure

  32. Agricultural tyres in practiceSummary inflation pressure • Effects of unadopted inflation pressure • increased fuel consumption due to higher rolling resistance • increased or uneven tyre wear (mainly on the road) • reduced traction due to increased slip • negative influence on riding comfort and stability • negative influence on the forward motion • damages to the turf and the soil structure

  33. Agricultural tyres in practice3. Wheel load & weight distribution Weight on a tractor

  34. Agricultural tyres in practice3. Wheel load & weight distribution • Reasons for additional weights on a tractor: • increase traction force • Example: • the optimal power/weight –ratio is 45-55 kg/hp, • a 360 hp tractor empty weight is ~10.500 kg 29 kg/hp • additional weight of 7.500 kg would be needed to optimize the • tractive force • balance the weight distribution • In general the front axle is unloaded by the weight of an implement attached to the rear end or by the force effect at high and substained torque (e.g. plough, grubber).

  35. Agricultural tyres in practice3. Wheel load & weight distribution Weight distribution of tractors Exampel: Tractor 150 HP-class Tractor weight (empty) G = 6.500 kg Weight distribution: FA 40%, RA 60% RearAxle weight = 3.900 kg FrontAxle weight = 2.600 kg Total weight allowed 10.000 kg RA: 650/65R38 AC 65 FA: 540/65R28 AC 65 Resulting wheel load: RA 1.950 kg FA 1.300 kg

  36. 2,0 m 1,5 m Agricultural tyres in practice3. Wheel load & weight distribution Weight distribution (road) Tractor weight (empty) G = 6.500 kg RA weight = 3.900 kg (60%) FA weight = 2.600 kg (40%) with additional weight G = 9.900 kg RA weight = 7.929 kg (80%) FA weight = 1.971 kg (20%) Wheelbase: 2,8 m Distance rear weight from RA 2,0 m Distance front weight from FA 1,5 m 2.600 kg 800 kg 2,8 m RA: 650/65R38 AC 65 FA: 540/65R28 AC 65 Resulting rear load: RA 3.970 kg FA 990 kg

  37. Agricultural tyres in practice3. Wheel load & weight distribution Weight distribution (field) With additional weights on road G = 9.900 kg Field G = 8.200 kg RA weight = 7.929 kg (80%) RA weight = 5.014 kg (61%) FA weight = 1.971 kg (20%) FA weight = 3.186 kg (39%) Resulting wheel load: RA 2.510 kg FA 1.600 kg 2.600 kg Thereof approx. 1/3 as remaining axle weight 800 kg 1,5 m 2,0 m 2,8 m RA: 650/65R38 AC 65 FA: 540/65R28 AC 65

  38. Agricultural tyres in practice3. Wheel load & weight distribution Weight distribution

  39. Agricultural tyres in practice3. Wheel load & weight distribution „Caught“ on the way to work: Fendt 815 Vario TMS Full spreader, weight ca. 3,5 t RA tyres 650/65R42 Driving speed +/- 50 km/h Driving distance ca. 20 km Inflation pressure RA real 1,3/1,1 bar target* min. 1,6 bar (* with approx. 9.000 kg on the RA) Using tyre size 710/70R38 1,2 bar would have been sufficient.

  40. Agricultural tyres in practice3. Wheel load & weight distribution • Effects of wrong weight distribution • increased fuel consumption • increased or uneven tyre wear • reduced traction • negative influence on the driving stability • negative influence on the forward motion

  41. Agricultural tyres in practice Thanks for your attention…

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